The following preparations containing an insulin sensitizer such as thiazolidinediones and an insulin secretagogue were reported:
1) a pharmaceutical composition comprising an insulin sensitivity enhancer in combination with one or more antidiabetics differing from the enhancer in the action mechanism (see EP 749751 A);
2) a composition comprising synergistic effective amounts of a sulfonylurea antidiabetic agent and glitazone antidiabetic agent (see WO 98/36755);
3) a pharmaceutical composition containing an insulin sensitizer, an insulin secretagogue and a pharmaceutically acceptable carrier (see WO 98/57649); and
4) a pharmaceutical composition containing an insulin sensitizer, a sub-maximal amount of an insulin secretagogue, and a pharmaceutically acceptable carrier (see WO 99/03476).
It is preferable that in a solid preparation comprising an insulin sensitizer and an insulin secretagogue, the active ingredients are biologically equivalent to those which are contained in two separate solid preparations as a single active ingredient.
However, the present inventors found a problem in a solid preparation comprising an insulin sensitizer and an insulin secretagogue for the first time, that is, found that said solid preparation had the undesirable dissolution property of an insulin secretagogue, that is, the dissolution rate of an insulin secretagogue from said solid preparation was slower as compared with that from “a solid preparation containing an insulin secretagogue as a single active ingredient”.